These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Game Breaker: Any sufficiently powerful form can become this, such as any 6-limb Rage color, but the real winner here is the Rejuvinator item. Without the Rejuvinator, the game is somewhat difficult but not unbearable. With a supply of Rejuvinators, the game gets completely snapped in half as you basically can't die.
Nightmare Fuel: The player Cubivore's increasing wildness and sanity slippage.
That One Boss: The District Attorney Beast: Controls Scenturions instead of Scentipedes, and while you were on the giving side of most Curb Stomp Battles, you'll easily be on the recieving side.
That One Level: The first level of the bird lap pits you against a pack of 2-limbed dark greyodons while you're still a pathetic one limb.
Wake Up Call Boss: The Boyscout Beast, as a Bluocyte, has an impressive pouncing range, and can take off a large amount of your health with just one pounce. It can also duck into the water to hide, should it feel threatened, making damaging it difficult.